A recent Workshop on Lung Function and Dysfunction in Infants and Children sponsored by the National Heart, Lung and Blood Institute emphasized the critical need for methods of assessing pulmonary function in infants and young children. Currently, investigators cannot assess the efficacy of therapy modalities in this patient population because there is no method for measuring their pulmonary function. In Phase I we investigated two pulmonary function tests for infants that are noninvasive, and require no patient cooperation and minimal patient contact. These tests are based on the mechanical impedance of the respiratory system which is computed from measurements of the flow response is measured at the airway opening (mouth and nose) by way of a face mask. Specific physiological parameters such as airway resistance are obtained from analysis of these data using systems identification techniques. Results from Phase I indicated that transfer impedance is very sensitive to changes in airway caliber induced by bronchoconstriction and bronchodilation in infants but input impedance is not. The long term goal of this effort is to develop a commercially available product based on transfer impedance measurements for the evaluation of pulmonary function in infants. To achieve this goal we will develop an improved prototype system (hardware and software) during the first year, and do extensive clinical evaluation of the system during the second year. PROPOSED COMMERCIAL APPLICATION: The proposed research and development will result in a unique pulmonary function test for infants and young children. This product will consist of integrated data acquisition and analysis methods that will provide information about the clinical status of the respiratory system. The need for such a test has been identified by a National Committee of Pediatric Pulmonologists.